This invention relates to a device to investigate the flow movement in cylindrical components, as installed especially for reciprocating piston engines, in order to analyze the charge movement generated during the intake process within the cylinder.
The known methods of measurement relate to the investigation of the swirl flows, the axis of rotation of which being parallel to the axis of the cylinder. These swirl flows are usually found in reciprocating piston engines having one inlet valve per cylinder. With such engine designs these swirl flows are generated within the cylinder during the suction phase of the intake process due to the common tangential port configurations.
For conventional reciprocating piston engines with two inlet valves per cylinder, which are arranged parallel to the axis of the crankshaft, no swirl flow of this type is generated because of the symmetrically constructed inlet systems. With such reciprocating piston engines a shape of flow dominates, the axis of rotation thereof being arranged at right angles to the axis of the cylinder. The effect of such flow movement of the combustion of the engine differs in principle from that of the swirl flow.
For the swirl flow the rotary speed components, which in the ideal model are constant after conservation of angular momentum during the compression phase, bring about a stabilization of the vortex. For shapes of flow where the axis of rotation is vertical relative to the axis of the cylinder, the main swirl decomposes into increasingly small partial vortexes due to the movement of the piston. This decomposition process transforms the rotational energy into additional turbulence, thus generating high turbulent energy with these shapes of flow.
The different kinds of charge movements have an effect on the combustion by affecting the flame velocity as the sum of the burning rate and transport velocity. Intensive flows with the axis of rotation vertical to the axis of the cylinder lead to an increase in the turbulent burning velocity, owing to the severe increase in turbulence during the compression phase, the consequence of which is a definite flattening off of the flame surface.
For swirl flows, thus for flows whose axis of rotation is parallel to the axis of the cylinder, the production of turbulence is less intensive owing to the slower decay of the swirl. The resulting lower turbulent burning velocity is supported naturally by a more intensive transport movement, which leads to the kernel of the flame growing faster immediately following the introduction of ignition in externally ignited reciprocating piston engines.
Even though both shapes of flow, thus swirl flows with the axis of rotation parallel to the axis of the cylinder and vortexes with the axis of rotation vertical to the axis of the cylinder, lead to faster combustion, the working mechanism is totally different.